Electronic security components processing sensitive information are used especially in smart cards. Applications of these cards include accessing banks for banking applications, and for remote payments for television, gasoline distribution and highway tolls, for example. These electronic security components have to process confidential data that must be shielded against any attempt at espionage for fraudulent purposes. The confidential data travels through the data bus of the component between a central processing unit (processor) and peripherals, such as memories.
Different methods can be implemented to discover these confidential data elements. In particular, one physical characteristic that can be observed external the electronic component is its current signature which depends on the passage of data in transit on the data bus. The data bus has a high capacity because it circulates throughout the component.
For this reason, the output interface includes three-state selection switches sized to let through high current for charging or discharging the line capacitor. Since the data bus is an 8-bit data bus, it includes eight large selector switches that are activated to apply a data element to this bus. Consequently, there is high current consumption during the selection switching of the switches.